Skeletal System

Functions Support Protection Movement Storage Hemopoiesis

Types of Tissue in System Connective: dense fibrous (ligaments, tendons) cartilage (ends of long bones, between vertebrae) hemopoietic (bone marrow) bone

Cellular Level Compact bone Spongy bone Cartilage

Compact Bone Outer layer Dense calcified matrix Structural units; Haversian Systems (osteons)

Haversian Systems Circular Multiple layers (resemble rings of an onion)

Haversian Systems Concentric lamella Central canal Osteocytes Lacunae Caniculi

Spongy Bone Porous Many spaces; filled with marrow hemopoiesis Trabeculae

Cartilage Looser matrix Flexibility Less dense Chondrocytes Collagen fibers in a firm gel Lacunae house chondrocytes NO direct blood supply (diffusion)

Endochondral Ossification Formed in cartilage How? Blood vessel invades Osteoclasts and osteoblasts function Starts in middle and at ends Continues from middle out to ends Epiphyseal line and plate

Bone Remodeling Bone formation from cartilage models Sculpting Osteoclasts; break down cartilage Osteoblasts; lay down calcium; bone forming cells Calcification process Lifetime event

Long Bone Structure Diaphysis; compact/lightweight (shaft) Epiphysis; ends/bone marrow Medullary cavity;middle/yellow bone marrow Articular cartilage; ends/joints Coverings and linings: Periosteum; covers outside except where articular cartilage Endosteum; lines medullary cavity

Divisions of the Skeleton Axial: midline (skull, spine, thorax, hyoid bone) Appendicular: appendages (extremities)

Axial Division Skull and Spine (vertebral column) and Thorax (ribs) SKULL Cranial bones (8) Face bones (14) Ear bones (6)

Thorax True ribs (14) attached to sternum False ribs (10) attached to cartilage, last two do not (floating ribs) Sternum (1) ; xiphoid process

Vertebral Column Cervical (7) Thoracic (12) Lumbar (5) Sacrum (1) Coccyx (1) (spine of an infant)